ci: enable vcpkg binary caching for Windows build

[DavidCozens]

Purpose

Speed up the Windows CI job by caching compiled vcpkg packages.

Change Description

Enable vcpkg's built-in GitHub Actions binary cache (x-gha). The vcpkg install cpputest step currently builds CppUTest from source on every run (~2 minutes). With binary caching, the first run populates the cache and subsequent runs pull pre-built binaries in seconds.

Uses actions/github-script to export the required ACTIONS_CACHE_URL and ACTIONS_RUNTIME_TOKEN environment variables, following vcpkg's recommended approach.

Test Evidence

No code changes — CI-only. The first run on this PR will populate the cache (same speed as before). The speedup will be visible on subsequent runs.

Areas Affected

.github/workflows/ci.yml — windows-build-and-test job only.

Summary by CodeRabbit

• Chores
  • Enhanced Windows CI pipeline efficiency through optimized binary caching, enabling faster and more reliable build processes.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 508f0193-2027-4e95-bbc9-611d8af4da52

📥 Commits

Reviewing files that changed from the base of the PR and between 8dd04f4 and add2678.

📒 Files selected for processing (1)

• .github/workflows/ci.yml

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📝 Walkthrough

Walkthrough

The Windows CI job in the GitHub Actions workflow is enhanced with vcpkg binary caching support by adding a job-level environment variable and a new step that exports cache-related credentials from the GitHub Actions environment.

Changes

Cohort / File(s)	Summary
Workflow CI Configuration .github/workflows/ci.yml	Added VCPKG_BINARY_SOURCES environment variable to Windows CI job and introduced a github-script step to export cache URL and runtime token for enabling vcpkg binary caching.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• ci: S13.1 Windows MSVC CI build #124: Original Windows vcpkg-based CI job that this PR enhances with binary caching configuration.

Poem

🐰 A rabbit hops through GitHub Actions fine,
With vcpkg caching, builds will shine,
The cache flows swift, no rebates lost,
Windows CI speeds up, worth the cost! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: enabling vcpkg binary caching for Windows CI builds.
Description check	✅ Passed	The description provides all required sections (Purpose, Change Description, Test Evidence, Areas Affected) with clear, specific information matching the actual changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ci/vcpkg-binary-cache

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_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[github-actions]

☀️   Quality Summary

   🚦   Unit Tests (GCC): 99% successful (✔️ 479 passed, 🙈 3 skipped)
   🚦   Unit Tests (Clang): 99% successful (✔️ 446 passed, 🙈 3 skipped)
   🚦   Unit Tests (Sanitize): 99% successful (✔️ 446 passed, 🙈 3 skipped)
   🚦   BDD Tests: 100% successful (✔️ 31 passed)
   🚦   Unit Tests (MSVC): 100% successful (✔️ 338 passed, 🙈 1 skipped)
   ⚠️   Clang-Tidy: No warnings
   ⚠️   CPPCheck: No warnings

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Created by Quality Monitor v1.14.0 (#f3859fd). More details are shown in the GitHub Checks Result.

[github-actions]

☀️   Quality Summary

   🚦   Unit Tests (GCC): 99% successful (✔️ 479 passed, 🙈 3 skipped)
   🚦   Unit Tests (Clang): 99% successful (✔️ 446 passed, 🙈 3 skipped)
   🚦   Unit Tests (Sanitize): 99% successful (✔️ 446 passed, 🙈 3 skipped)
   🚦   BDD Tests: 100% successful (✔️ 31 passed)
   🚦   Unit Tests (MSVC): 100% successful (✔️ 338 passed, 🙈 1 skipped)
   ⚠️   Clang-Tidy: No warnings
   ⚠️   CPPCheck: No warnings

---

Created by Quality Monitor v1.14.0 (#f3859fd). More details are shown in the GitHub Checks Result.